I've just been made aware that there are some items on my credit history that are not mine, the largest is for over $1000. I've never used a credit card or taken out a loan, so I can be sure they are not mine. What are the steps I need to take to resolve this?
This happened to me in college, I feel for you.
It's also popular advice to cancel your credit/debit card(s) and get new ones, or at least put a "check ID" directive on them by calling the card companies. Unless you've seen questionable activity there, don't worry about it. Credit/Debit skimming and other forms of card fraud are usually done by different criminals than the sort who quietly take out loans in your name, and bored cashiers rarely check ID even when the card comes back with a "check ID" flag.
If you are a student, check all of your college paperwork. A ton of identity theft happens to college students because many schools still have the inexcusable habit of printing your full SSN (sometimes along with your birthdate) on nearly every piece of paper they mail you. It's easy for someone to get a hold of your information that way. Of course, anyone's mail can get stolen, I've just seen some truly egregious behavior on the part of universities in this regard.
First thing you need to do is contact each credit bureau and place a credit freeze on your credit. This is different than fraud warnings and will actually stop a criminal rather than let criminal activity happen and send you a letter.
Use the credit bureau's systems to challenge the item on the report. I would do it via the web site AND send certified letters (so you have proof you sent them) to each bureau challenging the specific items. This might take 3 months or more to have an effect, but since the lender reporting to your credit won't be able to prove you took out the loan, the incorrect items will be removed from your report.
Follow up frequently. I would think a credit monitoring service for the next few months will allow you to see your report often to make sure things are falling off, and nothing bad is being added.
Remember it takes 60 days for something to be removed from your credit. Be vigilant, but be a little patient.
Is this a case where a relative with a similar name or roommate with the same address is getting confused for you, or a fraudulent act?
If it is the latter, in addition to the credit bureau stuff, you need to call your local police and get a police report filed.